<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        html, body {
            padding: 0;
            margin: 0;
        }
        .outer {
            width: 200px;
            height: 200px;
            border: 1px solid red;
            display: flex;
            justify-content: center;
            align-items: center;
        }
        .inner {
            width: 100px;
            height: 100px;
            background-color: #0366d6;
        }
    </style>
</head>
<body>
    <div class="outer">
        <div class="inner"></div>
    </div>
</body>
</html>